Light-emitting diodes (LEDs) are light-emitting devices manufactured in semiconductor materials. The devices have two electrodes. When a voltage is applied across the terminals, a small current will flow and the recombination of electrons and holes will release excess energy in the form of stimulated light. This is the fundamental light-emitting principle of LEDs. LEDs are different from general incandescent bulbs. They are luminescent, having the advantages of low power consumption, extended lifetime, no warm-up time, and fast response time. In addition, they are small in size, vibration enduring, and suitable for mass production, and they can be manufactured into an ultra small device or arranged in a matrix form. Currently, LEDs are popular in indicators and display devices of information, communication, and consumer electronic products, and have become indispensable devices of daily lives.
In order to enhance light-emitting efficiency of LEDs, nowadays, a reflection layer is set in the structure of LEDs for reflecting the light energy emitted by the LEDs and reducing energy loss. The materials of the reflection layer according to the prior art are mostly metallic materials. However, the reflectivity of the reflection layer using the metallic materials are inferior, causing the reflected light energy be absorbed by other material layers of the LEDs without enhancing light-emitting efficiency thereof. Besides, inter-diffusion phenomenon occurs between the reflection layer and other metal layers.
To solve the problems described above, a reflection layer comprised by a metallic material and a dielectric material is developed. However, the reflection layer can only improve the inter-diffusion phenomenon between the reflection layer and other metal layers. The reflectivity thereof is not enhanced. Hence, improvements in light-emitting efficiency are still limited.
Accordingly, the present invention provides a structure of reflection layer containing no metallic materials. The reflection layer can be applied to LEDs of various types, and can improve the light-emitting efficiency of LEDs.